The field of the invention is motorcycle engines and the invention relates more particularly to the tappet, or valve lifter or cam follower, assembly. In order to increase the potential RPM of a motorcycle engine it has been found that by providing additional downward pressure on the tappet assembly, instead of relying only on the spring of the rocker arm, additional RPM's may be developed. Devices have been designed to accomplish this purpose but are cumbersome and require modifying the engine to which it is being fitted. Furthermore, a unit providing the capability of increasing RPM safely with the compactness required was unavailable.